The present invention relates generally to an apparatus and method for providing heat to a subsea pipeline or other structure, and more particularly relates to a hydraulic friction fluid heater for providing heat to a subsea pipeline or other structure.
There often arises a need for heat to be supplied in a subsea environment. This frequently comes up in the offshore oil and gas industry. It is well known in the oil and gas industry that under certain pressure and temperature conditions the gases in a typical oil or gas well may form a solid hydrate or a solid wax within a pipeline. A hydrate is basically methane- or hydrocarbon-type ice. A wax is basically a paraffin-based solid formation. Hydrates and waxes are more likely to form under conditions of high pressures and low temperatures. Although hydrates and waxes may form at any water depth, hydrate and wax formation occurs more commonly in deep water. For example, at about 1000 feet and below, the water temperature remains relatively constant—just slightly above freezing in the vast majority of the world's oceans. The pressure, however, dramatically increases with depth, which affects hydrate and wax formation. In general, the deeper the water the more critical a problem hydrates and waxes become for oil company operators. Typically, hydrate and wax formation becomes an issue at approximately 500 meters (1500 feet), and below approximately 1000 meters (3000 feet) presents serious problems for oil companies.
The solid hydrate or wax forms a blockage inside a pipeline and reduces or completely blocks the product flow of oil and/or gas. Hydrate formations also occur at other locations, for example, externally on a subsea well head. Hydrates have also formed externally on the connector between a subsea wellhead and the lower marine riser package (“LMRP”) resulting in frozen latches that prevent the connector from releasing.
Some companies have attempted to address the hydrate issue by installing hydrate traps in their pipelines. The hydrate trap is basically a loop inside the pipeline that is specific to hydrate remediation. The installed hydrate trap is intended to generate the heat to remediate the hydrate plugs or ice. However, hydrate formation is a problem for existing subsea pipelines having no hydrate traps as well as for subsea well heads and associated equipment mounted thereon.
Typically, when working in the subsea environment at significant depths, remotely operated vehicle (“ROV”) systems are used. ROV systems are typically hydraulic-operated. In the past, attempts have been made at subsea hydrate and wax remediation with the use of electric heaters powered by an ROV system, however, typical ROV systems do not have sufficient electrical power to generate the heat necessary to effectively remediate such formations.
What is needed is a method and apparatus for performing subsea hydrate and wax remediation using heat. It is also desirable to have an apparatus and process for performing subsea hydrate and wax remediation using heat produced hydraulically. It is further desirable to have an apparatus and process for performing subsea hydrate and wax remediation using heat produced subsea. Additionally, it is desirable to have an apparatus and process to produce heat subsea using existing remotely operated vehicle (“ROV”) systems.